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Completley confused about Southbend

Hey there im working on an older Southbend steam kettle (KSLG-40e) and im completely mystified as to how this flame sensor works. It uses a Honeywell electronic ignition system and there is no detectible flame sensor or thermocouple. I spoke with a tech at Southbend and he told me to check the millivolts on the ground wire of the ignition module which grounds to the gas valve.
The only wire running to the pilot/ignitor is the ignitor wire and there are no other sensors. The only explanation the tech gave me was "dissimilar metals". I understand the whole dissimilar metals issue what i dont understand is how the gas valve generates the needed millivolts for the Honeywell to detect the flame with no connection other than the pilot light tube.

Even in millivolt gas valves there are several configurations depending on manufacturer. Then there are gas valves like you seem to be talking about that are electronically lit by a spark. The spark ignitor doubles as the flame sensor and the ignition module reads the millivolts that travel back when the ignitor is heated by the flame. A very light cleaning with a green scotchbrite pad helps also removing and cleaning the entire pilot assembly to ensure it is grounded to the metal it attaches to. If I'm on the right track with the design you're talking about you should be looking for the voltage after ignition traveling to the gas valve. Is this an intermitant pilot or just burner ignition as difrferent tests are used to check out the various components?

Thanks for the reply and info, that clears up my " how it works" confusion.
The pilot lights first then the burners then both go out at once after about 60 seconds. This repeats for a few cycles and then either quits completely or it works, most often the flames extinquish untill power is cycled and it starts over again.